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KEY POINTS
Two-and three-dimensional fetal and neonatal neurosonography is an informative, noninvasive, and inexpensive modality that is of great benefit in clinical diagnosis.
As technology improves and our understanding of sonoanatomy of the fetal and neonatal brain widens, the distinction between normal and abnormal, as far as anatomy is concerned, becomes increasingly possible.
Anomalies and disease of the developing brain area are common. In order to diagnose a deviation from what is normal, it is important to understand and recognize the developmental milestones of the normal brain, how it grows and matures, reaching its almost final anatomy at birth.
This chapter presents the 2D and 3D ultrasound tools as well as the sonographic landmarks of the normal developing embryonic and fetal CNS and also suggests new ways to study it systematically.
The introduction of TVS in fetal neurosonography adds an additional powerful tool to the diagnostic algorithm, increasing diagnostic precision in patients suspected of an anatomically abnormal fetal CNS.
Unlike in our third edition, we have integrated the previously separate sections dealing with the 2D and the 3D fetal brain anatomy. We believe they are inseparable, and both are necessary to understand the development and pathologies of the fetal brain.
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Problems of the central nervous system (CNS) can range from very simple—that is, merely a variance of the normal—to the most devastating diseases incompatible with life. It is important to recognize these anomalies as the fetus is scanned throughout gestation, starting very early in the first trimester to late in the third.
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The prerequisite for differentiating normal from abnormal structures is a thorough knowledge of the CNS anatomy. It is beyond the scope of this and the following chapters to teach the reader advanced neuroanatomy; however, special emphasis is placed on describing basic but sufficiently detailed sonographic neuroanatomy to recognize structures seen by 2D and 3D transabdominal (TAS) or transvaginal sonography (TVS). It is not sufficient to know only the anatomy of the full-term fetal or neonatal brain. Those interested in scanning the fetal brain to detect deviations from the norm may have to first refresh their knowledge of the fully formed adult neuroanatomy to be able to apply it to the fetus.
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Dealing with the sonographic anatomy and pathology of the fetal brain requires an additional dimension that is of the utmost importance for correctly evaluating the CNS at various prenatal ages of the fetus, that is, knowledge of the evolution of structures from about 6 to 7 postmenstrual weeks to the time of birth. Almost all organs and organ systems are in place by the end of the embryonic period. However, only at approximately 14 to 16 postmenstrual weeks some of them—the heart and the kidneys, for example—perform at their final level of perfection.
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All that most organs do during the fetal period is increase in size. The brain, on the other hand, undergoes major developmental changes ...